If I were you, I'd switch to warlock right after WoTLK popped in. Mages have super dull, almost braindead pve gameplay in every spec, neither engaging nor challenging enough to be interested. Try Affliction - the iconic Warlock spec. Or Demo, if you don't afraid of being lost in the buttons. Don't touch Destro, its practically as dull as a mage.

It's funny OP, I still play wow, but have played mage since wrath, and want to start raiding again, probably next expac, and I too am thinking about making the switch to Warlock, I am also considering Shaman, I have a level 90 one, and it's pretty cool. I think you'll agree with me on this though, once you play mage every other class feels insufficient without your blink.

I've played a destruction lock since about 4.0, before that affliction mostly since vanilla. never really liked or played demo.

Destro is not boring. I've recently started leveling a mage alt just to help my guild get the classy achivements, and so far im finding it boring as hell compared to my lock main. its basically warlock lite in terms of mechanics and it just feels so slow.

I've played a destruction lock since about 4.0, before that affliction mostly since vanilla. never really liked or played demo.

I agree. Kinda hated Demo since Vanilla, and probably will never really touch it. Don't like the flavour of it.

And no, I too think that it's definitely not boring (otherwise I wouldn't play it for so many years now exclusively)
It's just different from the other two specs, and sometimes feels a bit more mage-ish.
(which isn't new, though - Vanilla fire destro in naxx says hi )

OP - What you're probably beginning to figure out is that there is a pretty sharp divide in the Lock community between Destro, Affliction, and Demo. That's to Blizzard's credit, IMO, that they came up with three playstyles that are so distinct that you have people actually hating one and loving another.

I simply love Destro because almost all the decisions are Meta decisions. If you like micromanaging a bunch of buttons and timers (and clearly some people absolutely love that and feel it's the pinnacle of gameplaying - just not me) then Affliction or Demo may be better for you. Also, our AoE just feels like "muwahahaha everything dies with fire!! KABOOM KABOOM KABOOM!!!!" And there's nothing like sending off a stream of "Die NOW!!!" Chaos Bolts with trinket procs aligned (something that's fairly difficult to pull off . . . again a meta decision challenge). Havoc and Shadowburn executing adds simply multiplies the fun. (There's nothing like the feeling of "I KILLED IT WITH A BOOM!" . . . also every time I hear the Shadowburn sound it sounds like I'm wiping out the rest of their life force, which is pretty awesome).

All three specs have been competitive throughout MoP (something I can't say for any other class TBH). Yes, one is always "higher" than the others, but all have been competitive (especially at the beginning of tiers, where it actually matters), if that matters to you.